1. Field of the Invention
This invention relates generally to semiconductor manufacturing, and, more particularly, to a method and apparatus for performing film stack fault detection using optical data.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today""s manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Generally, a set of processing steps is performed on a group of semiconductor wafers, sometimes referred to as a lot, using a semiconductor manufacturing tool called an exposure tool or a stepper. Typically, an etch process is then performed on the semiconductor wafers to shape objects on the semiconductor wafer, such as poly-lines, which are conductive lines that connect one conductive region on the semiconductor region to another. The manufacturing tools communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which a manufacturing network is connected, thereby facilitating communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process.
FIG. 1 illustrates a typical semiconductor wafer 105. The wafer 105 typically includes a plurality of individual semiconductor die arranged in a grid 150. Photolithography steps are typically performed by a stepper on approximately one to four die locations at a time, depending on the specific photomask employed. Photolithography steps are generally performed to form patterned layers of photoresist above one or more process layers that are to be patterned. The patterned photoresist layer can be used as a mask during etching processes, wet or dry, performed on the underlying layer or layers of material, e.g., a layer of polysilicon, metal or insulating material, to transfer the desired pattern to the underlying layer. The patterned layer of photoresist is comprised of a plurality of features, e.g., line-type features, such as a polysilicon line, or opening-type features, that are to be replicated in an underlying process layer. Using the processes described above, a plurality of film layers are stacked to create a film stack, which leads to the production of integrated circuits on a semiconductor wafer.
Generally, a plurality of layers is formed on a semiconductor wafer using various materials such as polysilicon material, insulating material such as silicon dioxide, and the like. Ultimately, features of semiconductor devices will be formed in these layers using known photolithography and etch processes. In order to create various features of a semiconductor device, such as a transistor, a plurality of film stacks are formed. For example, a gate electrode may be patterned from a film stack comprised of a layer of polysilicon formed above a gate insulation layer that is formed above a silicon substrate. Another example of a film stack may comprise a layer of polysilicon and a layer of silicon oxynitride stacked on a silicon substrate.
Due to the complexities of manufacturing facilities, tracking the characteristics of film stacks may be difficult. A particular film stack may be sent through various processing steps. At the same time, a different film stack may also be processed by the same manufacturing facility. It is important that an accurate characterization of the film stack is available before a particular process, such as an etch process, is performed on the film process. Using current methodology, generally, film stacks are characterized by the thickness of the films in the film stack. Using this characterization, fault detection is performed on the semiconductor wafers being processed. However, without an accurate characterization of the film stack, an efficient fault detection analysis is difficult.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided for performing film stack fault detection. At least one semiconductor wafer is processed. Metrology data from the processed semiconductor wafer is acquired. Data from a reference library comprising optical data relating to a film stack on the semiconductor wafer is accessed. The metrology data is compared to data from the reference library. A fault-detection analysis is performed in response to the comparison of the metrology data and the reference library data.
In another aspect of the present invention, a system is provided for performing film stack fault detection. The system of the present invention comprises: a computer system; a manufacturing model coupled with the computer system, the manufacturing model being capable of generating and modifying at least one control input parameter signal; a machine interface coupled with the manufacturing model, the machine interface being capable of receiving process recipes from the manufacturing model; a processing tool capable of processing semiconductor wafers and coupled with the machine interface, the first processing tool being capable of receiving at least one control input parameter signal from the machine interface; a metrology tool coupled with the first processing tool and the second processing tool, the metrology tool being capable of acquiring metrology data; a film stack optical data reference library, the film stack optical data reference comprising optical data related to a plurality of film stacks; and a film stack data analysis unit coupled to the metrology tool and the film stack optical data reference library, the scatterometry data film stack data analysis unit capable of comparing the metrology data to corresponding data in the film stack optical data reference library and calculating at least one film stack error.